1. Field of the Invention
The present invention relates to a spherical rotary piezoelectric motor, and more particularly, to a multi degrees of freedom rotary traveling wave piezoelectric motor.
2. Description of the Related Art
Generally, piezoelectric motor has the advantages of small size, light weight, less noise, high thrust at low speed, high holding force, fast response, and no EMI problem, and so on. It has been widely used in many areas such as digital still camera, watch, automobile, robot, micro positioning system, medical device, aerospace, and micro machinery, etc.
In order to achieve multi degrees of freedom by using piezoelectric motors, a few implementations have been proposed, such as (1) using piezoelectric actuators to support and to drive a spherical rotor so as to control the motions of the spherical rotor, this type of piezoelectric motor is used as the device of Scanning Electron Microscope (SEM); (2) using multi disc-type piezoelectric actuators to drive a spherical rotor, since each piezoelectric actuator is driven with a different vibration mode, therefore, multi degrees of freedom is achieved by mixing different vibration modes (as stated in Taiwan patent No. I288523); and (3) using three sets of ring-shaped piezoelectric actuators implemented with equal spatial distance to drive a spherical rotor to achieve three degrees of freedom, this type of piezoelectric motor is used in multi-axis mechanical manipulators or CCD surveillance cameras.
Although the present piezoelectric motors provide various advantages and functions, the implementations of the above-described piezoelectric motors are still complicated; therefore, it is necessary to provide a simple rotary piezoelectric motor design which can achieve multi degrees of freedom.